Here are some examples of how it can be used:
* Joyeux Noël! (Merry Christmas!)
* Joyeux anniversaire! (Happy Birthday!)
* Elle a l'air joyeuse. (She looks merry.)
* C'est une fête joyeuse. (It's a merry celebration.)
You can also use gaie (pronounced "gay") which means "cheerful" or "happy".